Summer watering to cool roots

[PastryBaker]

Yes,,,another watering question. Groundbreaking.
I always water early in the morning all year. And twice a day in late summer.

Since it gets so freaking hot here in summer (110-123F), I was wondering if it would be beneficial to water later in the day to help cool the roots?
I mean if they need it in the morning, then I would do that.

I am off all summer, and have been watering in the morning and then misting a couple times a day.
All of my trees are under 70% shade cloth.

Thanks

 

[Wires_Guy_wires]

It would be beneficial to water later in the day, yes. Depending of course on how much water they require.
But a constant source of evaporation would be better, it doesn't need to be the soil itself, it can be the surrounding air too; a wet towel will probably be beneficial too. Or watering trays, the stuff we all hate in wet areas of the world might just save your plants on a hot day.

We don't get these high temperatures a lot, so I water in the evening and check the soil in the morning. Usually my evening waterings are enough to allow the soil to evaporate the whole day. One thing to keep in mind is that water does not evaporate inside water, it needs air to move to, so having a constantly wet soil would just mean it'll heat up like a bowl of soup in a microwave.

Clay types might be interesting to look at too. Terra cotta clay for instance breathes much more than japanese made pottery (due to firing temps and all) and it's known to be beneficial to cooling, it would mean you'd have to water more though. Since it's about the oldest and most used "clay type" in the world, I feel like we're not doing it justice by keeping it out of bonsai.

 

[stubmle]

I don't have a link, but I recall someone posing a similar question on here a while ago and taking some temperature readings to test it. If I recall correctly, they found that watering did reduce pot temperature significantly... but not for very long. Within a few minutes the soil temp had got back up to its previous value.

Likes Wires mentions, passive cooling is probably a more practical approach.

 

[Wulfskaar]

This might be dumb, but I've thought of putting some white duct tape on my black nursery pots and/or white cloth loosely around the soil/pots on days when you could easily cook an egg on a car hood. I fear the black pots are too hot for the roots on the hottest days.

One of my cats is mostly white with black spots. She loves basking in the sun. When I pet her, the black spots are super warm, while the white is not.

 

[leatherback]

common practice to put wet cloth over pots in full sun during hot days.
I like to wet all my trees and surrounding area on very hot days. Assuming I am home.

 

[Bonsai Nut]

If you are under 70% shade cloth, do you feel you really need it? I suppose it would depend on the tree; California junipers grow in the Mojave, for example, and many conifers thrive in hot conditions. We never got as hot as Palm Springs in the OC, but I never found myself watering because of root heat concerns.

 

[rockm]

Place old wet white bath towels or hand towels over the soil surface and down the sides of the pot. Water THE TOWELS down to cool the roots. constantly watering soil and roots in really hot weather can lead to root rot as the root zone doesn’t dry down adequately. Trees can also slow down in hot weather —some native trees can enter something of a summer dormancy

 

[roberthu]

Watering to cool the roots down is risky. 70% shade cloth should be enough in most of the US. If you have the pots out of direct sunlight, you really shouldn't have too much issue.

 

[leatherback]

risky

why so.

 

[PastryBaker]

It would be beneficial to water later in the day, yes. Depending of course on how much water they require.
But a constant source of evaporation would be better, it doesn't need to be the soil itself, it can be the surrounding air too; a wet towel will probably be beneficial too. Or watering trays, the stuff we all hate in wet areas of the world might just save your plants on a hot day.

We don't get these high temperatures a lot, so I water in the evening and check the soil in the morning. Usually my evening waterings are enough to allow the soil to evaporate the whole day. One thing to keep in mind is that water does not evaporate inside water, it needs air to move to, so having a constantly wet soil would just mean it'll heat up like a bowl of soup in a microwave.

Clay types might be interesting to look at too. Terra cotta clay for instance breathes much more than japanese made pottery (due to firing temps and all) and it's known to be beneficial to cooling, it would mean you'd have to water more though. Since it's about the oldest and most used "clay type" in the world, I feel like we're not doing it justice by keeping it out of bonsai.

Thanks so much. Do you mean a wet towel on the top of the soil? Originally I was thinking of getting a misting system on a timer. It would go on for a minute or so every so often, but not directed on the soil.

 

[PastryBaker]

Place old wet white bath towels or hand towels over the soil surface and down the sides of the pot. Water THE TOWELS down to cool the roots. constantly watering soil and roots in really hot weather can lead to root rot as the root zone doesn’t dry down adequately. Trees can also slow down in hot weather —some native trees can enter something of a summer dormancy

Sounds good. And we do get trees going into summer dormancy. They are just trying to make it through the day and not having any new growth.

 

[PastryBaker]

If you are under 70% shade cloth, do you feel you really need it? I suppose it would depend on the tree; California junipers grow in the Mojave, for example, and many conifers thrive in hot conditions. We never got as hot as Palm Springs in the OC, but I never found myself watering because of root heat concerns.

They are in the sun about 7 hours and under 70% shade. Last year they did ok. But back then I didn't know anything about roots getting hot.

 

[Wires_Guy_wires]

Thanks so much. Do you mean a wet towel on the top of the soil? Originally I was thinking of getting a misting system on a timer. It would go on for a minute or so every so often, but not directed on the soil.

On the soil or even just hanging near it. A misting system might work too, but keep legionella in mind and either keep it active or let it run for a while before you get close to the mist.

 

[PastryBaker]

On the soil or even just hanging near it. A misting system might work too, but keep legionella in mind and either keep it active or let it run for a while before you get close to the mist.

Funny you say that. Many bars and restaurants here in the desert use misters to keep people cool. My friends laugh at me because I cover my drink when I am near the misters because of that bacteria. I am sure very few places clean their mister heads. And yes, I may be a bit crazy doing that. Originally I was a microbiology major.

 

[roberthu]

why so.

The pots get hot quickly if exposed to direct sunlight in the summer. To keep the pots and soil inside of them cool by watering means very frequent spraying and that can lead to overwatering easily. Root rot in hot summer is usually death sentence for most trees.

 

[ShadyStump]

I don't know about Southern California, but here it's a fairly hard rule to only water in the morning, or at least early enough that things can dry out before dark. Powdery mildew can be a serious problem, and any moist, dark spots can get hit hard. One of those things where once you see it, it's already too late.

I have all of my trees up against the western privacy fence where there's a modicum of afternoon shade, and I wet the benches and fence when I water. This helps keep humidity up for a good part of the day, and reduces temperatures for much of it. When it finally gets hot enough in that spot to worry, it doesn't stay hot long enough to worry.
Of course, way up here it's less the heat and more solar radiation that's a problem. Allot less atmosphere to mellow out the sun's rays at altitude.

 

[rodeolthr]

For those who've not spent any time in Palm Springs during summer, it presents a very unique environment where growing anything is concerned. During the peak of the summer heat, which can last for weeks, daytime highs of 110-120F mean that temperatures can still be in the high 90s at midnight. Anything you grow there needs to be able to handle that heat, sun or shade. The ambient temperature will not change by watering, except for a few minutes during evapororational cooling. So in my estimation, aside from shade, the most important thing is just the regular watering routine you have....and growing those plants which can take the heat.

 

[bonsaichile]

They are in the sun about 7 hours and under 70% shade. Last year they did ok. But back then I didn't know anything about roots getting hot.

And neither did the roots. If your trees are doing fine, follow their cue

 

[Ruddigger]

I’m watering 4x a day minimum right now in the Inland Empire.

 

[Ruddigger]

For those who've not spent any time in Palm Springs during summer, it presents a very unique environment where growing anything is concerned. During the peak of the summer heat, which can last for weeks, daytime highs of 110-120F mean that temperatures can still be in the high 90s at midnight. Anything you grow there needs to be able to handle that heat, sun or shade. The ambient temperature will not change by watering, except for a few minutes during evapororational cooling. So in my estimation, aside from shade, the most important thing is just the regular watering routine you have....and growing those plants which can take the heat.

Added to that Palm Springs gets crazy hot wind. It’s like living in a sand blaster. I used to work out there years ago.